New research aims to help fruit growers battling the dreaded Spotted-wing drosophila

Spotted Wing Drosophila, Drosophila suzukii

By Heidi Happonen

The Spotted-wing drosophila (SWD; Drosophila suzukii) is a notorious pest that feeds on ripening soft-skinned fruits such as blueberries, cherries, and peaches. Controlling it is difficult for a host of reasons, including its short generation time, wide range, lack of natural predators, and even its hearty immune system. Some estimates have suggested that the SWD is responsible for nearly $500 million in yearly crop damage in California, Oregon, and Washington alone[1].

Timothy Warren and his colleagues in the College of Agricultural Sciences’ Department of Horticulture at Oregon State aim to combat the SWD by better understanding its behavior. Warren recently received a $450,000 grant from the National Institute of Food and Agriculture (NIFA) to study the pest, along with colleague Vaughn Walton.

A neuroscientist with a Ph.D. from University of California, San Francisco, Warren is fascinated by how animals’ brains produce and maintain complex behavior. His current research focus is on the flight behavior of various Drosophila species, including SWD.

Prior research by Warren and colleagues has shown that even tiny fruit flies possess the sophisticated navigation capacities of larger insects like the monarch butterfly. They may be able to use this navigation capacity to disperse long distances.

“People often think of small insects like the SWD as flying randomly around in place, not moving anywhere.” Warren explained, “Our research aims to challenge this dogma.”

But because the insect is so small, its movement cannot be tracked in the field directly. Warren’s funded research will instead use a set of interrelated experiments to study the fly’s movement, including computerized camera traps in the field and flight simulators in the lab. Together, these studies will provide a quantitative understanding of how the SWD moves, which then can be used to manage the pest.

One aspect of understanding how the insect moves is to understand how it naturally arrives at its targets. Whereas the fly’s long-distance flight navigation may be in relation to the sky, when and where it decides to land is likely driven by smell.

The research Warren and his team are undertaking aims to address some of the crucial, unanswered questions about the behavior and physiology of this pest, allowing for more precise application of pesticides and bio-controls as well as better synthetic attractants to lure SWD away from important crops.

What’s more, studying the flight behavior of the SWD may have general applications to understanding animal movement in response to extreme climates.  For example, one possible reason the SWD is so challenging to combat is its potential rapid evolution and adaptation to surrounding environments. Recently, the pest has shown up in climatically inhospitable places like the Mojave Desert and high elevations in Oregon. It is unknown if the insect could migrate in response to extreme temperatures, which would allow it to respond to climate change.

Therefore, as scientists like Warren look to solve the immediate challenge of crop infestation by better understanding the behavior of the SWD, their research could shed light on larger questions of how animals are responding to a changing climate.

[1] Drosophila suzukii (Diptera: Drosophilidae): invasive pest of ripening soft fruit expanding its geographic range and damage potential DB Walsh et al Journal of Integrated Pest Management 2011

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